EVGNEWS Issue 2 2014

While wafer-to-wafer fusion bonding has predominately been used for high-volume manufacturing (HVM) of backside illuminated (BSI) image sensors, front-end-of-line 3D device stacking as well as novel BSI image sensors demand improved overlay alignment. Fusion bonding is moving up in the manufacturing value chain, with a strong pull-in from integrated device manufacturers and foundries.

The GEMINI FB XT is EVG's latest-generation fusion bonding equipment dedicated for HVM applications. The integration of essential pre-processing steps, optimization of process flows and productivity has been central objectives for the GEMINI FB XT. For this reason, capacity for pre- and post-processing modules has been added in the GEMINI FB XT.

Leveraging EVG's XT Frame platform, which is utilized across the spectrum of the company's industry-leading systems, the GEMINI FB XT provides a throughput increase of up to approximately 50% over the previous-generation platform. Integrated process steps consist of wafer cleaning and/or light chemical surface treatment, plasma activation and wafer bond alignment. Most important, the system incorporates EVG's new SmartView®NT2 bond aligner, which has demonstrated face-to-face alignment within 200nm (3σ)-exceeding the requirements of the latest edition of the Industry Technology Roadmap for Semiconductors (ITRS). Integrated metrology has also been added into the tool, which validates alignment after pre-bonding to enable customers to quickly fine-tune the bonding process for HVM processing if necessary.

Enabling Future Devices - Bonding and stacking of different wafers with high through silicon via (TSV) density is gaining importance due to the potential of 3D stacked devices in enabling higher bandwidth, lower power consumption and higher performance. Improving wafer-to-wafer fusion bonding accuracy to below 200nm (3σ) opens up the possibility of numerous novel stacked devices that incorporate these benefits, including stacked DRAM, memory-on-logic and next-generation CMOS image sensors.

Enabling New Bonding Technology - Recently, hybrid wafer bonding found its first adoption in BSI image sensor manufacturing, where it has helped to enable faster image readout and advanced image processing. Hybrid wafer bonding carries high potential for numerous other applications as well. EVG's GEMINI FB XT combines all the necessary features to bring hybrid bonding in high-volume production.

Optimized for HVM FEOL Environment - To support the migration of wafer bonding upstream in the manufacturing value chain, EVG has optimized the GEMINI FB XT for ultra-high throughput and productivity. Additional pre- and post-processing modules have been added for wafer cleaning and surface preparation, plasma activation and wafer bond alignment that enable increases in throughput by up to 50 percent. As a result, system productivity and efficiency of cleanroom space are optimized at the same time.